Technological advancements have provided neurosurgery with new paradigms for the restoration of neural function. The dual emergence of accurate stereotaxis and deep brain stimulation (DBS) have generated a revolution in the application of targeted neuromodulation applied to movement disorders, epilepsy, eating disorders, obsessive compulsive disease, and pain (Appendix C). Nonetheless, because DBS depends on the focused delivery of electric current, it is incapable of pharmacological specificity. Rather than delivering electric current, viral vectors can alter synaptic function with molecular specificity. Further, vector tropism can be modified, creating the potential for system specific neuronal gene delivery. The experiments outlined in this proposal attempt to develop a vector capable of both neural tropism and neuromodulation. To test these concepts, we propose to develop a recombinant adeno-associated virus (rAAV) capable of synaptic inhibition and motor neuron tropism. We have chosen the spinal reflex arc as a simple mammalian functional system amenable to neuromodulation. In addition, the functional disorder, spasticity, provides a target for the study of applied neuromodulation. We hypothesize that an rAAV vector capable of specific motor neuron inhibition will have therapeutic efficacy in animal models of spasticity. In addition to providing a novel approach to spasticity, data from these studies will permit the rational design of rAAV vector(s) for application to motor neuron disease (ALS) and stereotactic neuromodulation. There are 3 Aims: 1) Construct novel vectors capable of focused synaptic inhibition, 2) develop strategies for targeted gene delivery to motor neurons with rAAV, 3) apply targeted rAAV capable of synaptic inhibition in models of spasticity. The applicant has developed a focused interest in the neural basis for behavior in both normal and pathological states. His early training in simple systems neurophysiology, and later training in biochemistry and molecular biology have prepared him for a career in the study of focused gene-based neuromodulation. His appointment to the Cleveland Clinic Foundation will give him access to one of the most active programs in Functional Neurosurgery, and create opportunities for clinical application of his work.